JP2551748B2 - Motor speed controller - Google Patents

Description

The present invention relates to a speed control device for a motor.

"Problems with conventional technology" When controlling the speed of the motor by the rotation detection feedback pulse signal of the motor, the feedback pulse signal is F / V converted to bias the speed setting voltage, or the comparison calculation processing is performed to control the speed. Such a method is known as a so-called F / V conversion method. F / V like this
According to the conversion method, in order to obtain stability during low-speed rotation of the motor, an encoder with a large number of pulses per rotation is required, and since this F / V conversion method has an integration circuit, There is a problem that the response time is obstructed by the time constant of the circuit and it becomes a factor of rotational vibration. To prevent such rotational vibration, a compensating circuit is required, which makes the circuit configuration complicated and There was a problem of causing high costs.

"Means for solving the problem" The present invention, therefore, does not rely on the conventional F / V conversion method, but superimposes the rotation detection feedback pulse signal of the motor on the speed setting reference voltage and integrates it to obtain the set speed. The configuration is such that the speed control for the motor is performed by the set voltage synthesized at the corresponding pulse intervals. According to such means, the response and the feedback pulse signal with a low detection pulse number per one rotation of the motor can be provided. It is characterized in that it can provide a motor speed control device with excellent stability at low cost.

[Embodiment] The drawings are block diagrams showing one embodiment of a motor speed control device according to the present invention. In FIG. 1, 1 is an AC motor, and 2 is for detecting the rotational speed of the motor 1. Of the pulsating current voltage A detected by the magnetic sensing element 2.
2 is shaped into a rectangular wave B by the rotational speed detection pulse circuit 3 and outputs a motor speed detection signal C which is a pulse signal proportional to the rotational speed of the motor at each edge of the rectangular wave B, as shown in FIG. To do. As a result, the motor speed detection signal C that is the output is directly subtracted without F / V conversion, and as a result, the speed voltage signal D that is proportional to the difference between the set speed and the detected speed is output. The low pass filter 6 smoothes the ripple of the speed voltage signal D and outputs a control voltage G for determining the phase level. Reference numeral 7 is a comparator, 8 is a load current zero cross signal circuit, and 8 is a comparator amplifier. The comparator 7 is reset by the zero-cross pulse I via the circuit 10 and outputs another duty signal J for phase control according to the level V of the control voltage G output from the low-pass filter 6 to the motor phase. It is output to the control circuit 9. The motor phase control circuit 9 composed of a transistor, a thyristor, a triac, etc., is driven by the duty signal J by the comparator 7 and gives an output voltage K to the motor 1 to control its speed. When the motor 1 is of the AC induction type, the duty signal J from the comparator 7 outputs the zero cross pulse I for each AC half cycle of the load current, and accordingly the motor 1 for each AC half cycle.
Can be phase controlled with high accuracy.

According to such a speed control device for a motor, when the setting reference voltage is increased by the speed setting variable resistor 5, the speed voltage signal D obtained by comparison and integration with the output negative pulse C of the rotation speed detection pulse circuit 3 is obtained. Therefore, the level V of the control voltage G output from the low-pass filter 6 also rises, which reduces the duty signal J from the comparator 7 and acts to advance the phase to the motor phase control circuit 9. Therefore, the output voltage K of the circuit 9 is relatively increased and the rotation of the motor 1 is increased. Thus, when the rotation speed of the motor 1 increases,
Since the interval between the output negative pulses C of the rotation speed detection pulse circuit 3 becomes small, the average value of the speed voltage signal D in the comparison and integration amplifier circuit 4 decreases and the level V of the output control voltage G of the low pass filter 6 also decreases. As a result, the output duty signal J of the comparator 7 is increased to delay the phase with respect to the motor phase control circuit 9, and the output voltage K thereof is relatively decreased so that the rotation speed of the motor 1 is maintained at the set value. To It can be seen that when the set reference voltage is lowered, the motor 1 is maintained at the corresponding low rotation speed by the control operation opposite to the above.
Further, when the load of the motor 1 changes, the interval of the output negative pulse C of the rotation speed detection pulse circuit 3 based on the magnetic sensing element 2 changes, and accordingly, the level V of the control voltage G from the low-pass filter 6 also changes. The phase is controlled so that it fluctuates up and down to maintain the set speed.

When the motor 1 is a DC motor, the zero cross signal is given in the chopper cycle, so that the speed can be controlled by the chopper duty control of the DC motor.

As described above, the present invention regulates the control voltage for phase control by the voltage obtained by directly superimposing and integrating the speed setting reference voltage and the negative pulse proportional to the rotation speed of the motor. Since it is configured as described above, the responsiveness to load fluctuation is extremely high, and stable speed control is possible.
Further, according to the present invention, since there is no delay due to the integration of the F / V converter as in the conventional case, it is possible to respond quickly, so it is not necessary to use a high-resolution encoder or the like to obtain the rotation speed detection pulse, and therefore It is possible to provide a motor speed control device with excellent responsiveness and stability at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram of a speed control device for a motor according to an embodiment of the present invention, and FIGS. 2A to 2K are signal waveform diagrams of respective parts in FIG. 1: Motor 2: Magnetic sensing element 3: Rotation speed detection pulse circuit 4: Comparative integration amplification circuit 5: Variable resistor for speed setting 6: Low pass filter 7: Comparator 8: Load current zero cross signal circuit 9: Motor phase control circuit 10: Triangular wave generation circuit

Claims (1)

(57) [Claims] 1. A motor rotation speed is controlled by controlling an applied voltage or a supply current to the motor based on a voltage value obtained by comparing and amplifying a speed setting reference voltage and a motor speed detection signal. In the motor control circuit of the configuration, the motor speed detection signal is a pulse signal proportional to the rotation speed of the motor, the duty signal using a signal obtained through a low pass filter after subtracting the pulse signal from the speed setting reference voltage. And controlling the phase of the applied voltage or the supplied current to the motor by the duty signal.